RESUMO
Prion diseases are transmissible and progressive neurodegenerative disorders characterized by abnormal prion protein (PrPSc) accumulation in the central nervous system. Generation of synthetic PrPSc in a cell-free conversion system and examination of its transmissibility to animals would facilitate testing of the protein-only hypothesis and the understanding of the molecular basis of sporadic prion diseases. In this study, we used recombinant prion protein from a baculovirus-insect cell expression system (Bac-rPrP) and insect cell-derived cofactors to determine whether Bac-rPrPSc is spontaneously produced in intermittent ultrasonic reactions. No spontaneous generation of Bac-rPrPSc was observed at 37 °C, but when the reaction temperature was increased to 45 °C, Bac-rPrPSc was generated in all trials. Some Bac-rPrPSc variants were transmissible to mice, but when the reaction was repeated for 40 rounds, the transmissibility was lost. Notably, a variety of Bac-rPrPSc variants, including non-transmissible ones, differing in resistance to proteinase K and cofactor dependence during amplification, was generated under the same experimental conditions, including the same sonication settings and cofactors. However, their characteristics also disappeared after 40 reaction rounds and the variety converged onto a single variant. These results indicate that various Bac-rPrPSc variants with different transmissibility to mice and structural properties are generated, which compete with each other and gradually converge onto a variant with a slightly faster amplification rate.
Assuntos
Doenças Priônicas , Príons , Animais , Baculoviridae/genética , Baculoviridae/metabolismo , Insetos/metabolismo , Camundongos , Proteínas Priônicas/genética , Príons/metabolismo , Proteínas Recombinantes/metabolismoRESUMO
The baculovirus-insect cell expression system is a popular tool for the manufacturing of various attractive recombinant products. Over the years, several attempts have been made to engineer and further improve this production platform by targeting host or baculoviral genes by RNA interference. In this study, an inducible knockdown system was established in insect (Sf9) cells by combining an artificial microRNA precursor mimic of baculoviral origin and the bacteriophage T7 transcription machinery. Four structurally different artificial precursor constructs were created and tested in a screening assay. The most efficient artificial microRNA construct resulted in a 69% reduction in the fluorescence intensity of the target enhanced yellow fluorescent protein (eYFP). Next, recombinant baculoviruses were created carrying either the selected artificial precursor mimic under the transcriptional control of the T7 promoter or solely the T7 RNA polymerase under a baculoviral promoter. Upon co-infecting Sf9 cells with these two viruses, the fluorescence intensity of eYFP was suppressed by ~30â»40% on the protein level. The reduction in the target mRNA level was demonstrated with real-time quantitative PCR. The presented inducible knockdown system may serve as an important and valuable tool for basic baculovirus-insect cell research and for the improvement of production processes using this platform.
Assuntos
Bacteriófago T7/genética , Baculoviridae/genética , Lepidópteros/virologia , MicroRNAs/genética , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Bacteriófago T7/enzimologia , RNA Polimerases Dirigidas por DNA/metabolismo , Técnicas de Silenciamento de Genes , Engenharia Genética , Lepidópteros/genética , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Regiões Promotoras Genéticas , Proteínas Recombinantes/metabolismo , Células Sf9 , Proteínas Virais/metabolismoRESUMO
G protein-coupled receptors (GPCRs) exist in equilibrium between multiple conformations, and their populations and exchange rates determine their functions. However, analyses of the conformational dynamics of GPCRs in lipid bilayers are still challenging, because methods for observations of NMR signals of large proteins expressed in a baculovirus-insect cell expression system (BVES) are limited. Here, we report a method to incorporate methyl-13C1H3-labeled alanine with > 45% efficiency in highly deuterated proteins expressed in BVES. Application of the method to the NMR observations of ß2-adrenergic receptor in micelles and in nanodiscs revealed the ligand-induced conformational differences throughout the transmembrane region of the GPCR.
Assuntos
Ressonância Magnética Nuclear Biomolecular/métodos , Receptores Adrenérgicos beta 2/química , Coloração e Rotulagem/métodos , Alanina , Animais , Baculoviridae , Deutério , Insetos/citologia , Insetos/virologia , Bicamadas Lipídicas , Micelas , Ligação Proteica , Conformação ProteicaRESUMO
Biomarkers of cancer are often glycosylated membrane receptor proteins present on the cellular surface. In order to develop new antibodies for cancer diagnostics or treatment, it is a main pre-requisite that these target proteins are available in a native conformation. However, membrane receptor proteins are notoriously difficult to produce due to their hydrophobic nature and complex architecture. Here, we used the baculovirus-insect cell expression system to produce budded virus-like particles (VLPs) as the scaffold for the presentation of complex membrane proteins. Since the human epidermal growth factor receptor 2 (HER2) is known to be overexpressed in a number of cancers it was chosen as model for a tumor antigen. VLPs displaying full-length HER2 on the surface were produced in Spodoptera frugiperda 9 (Sf9) insect cells and purified by sucrose gradient ultracentrifugation. The number of secreted particles was quantified by nanoparticle tracking analysis. To confirm the presence of HER2 protein on the surface, VLPs were labeled with gold-conjugated antibodies and analyzed by transmission electron microscopy. Functionality of displayed HER2 was investigated by ELISA and a newly established biolayer interferometry based technique. Detection was accomplished using the specific monoclonal antibody Herceptin and filamentous phages displaying a single-chain variable fragment of an anti-HER2 antibody. Significant stronger binding of Herceptin and anti-HER2 phages to HER2-displaying VLPs as compared to control VLPs was demonstrated. Thus, we suggest that Sf9 insect cells are highly feasible for the fast and easy production of various budded VLPs that serve as a platform for full-length membrane receptor presentation.
Assuntos
Membrana Celular , Expressão Gênica , Receptor ErbB-2 , Vírion/química , Animais , Anticorpos/química , Membrana Celular/química , Membrana Celular/genética , Membrana Celular/metabolismo , Receptor ErbB-2/biossíntese , Receptor ErbB-2/química , Receptor ErbB-2/genética , Proteínas Recombinantes/biossíntese , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Células Sf9 , SpodopteraRESUMO
Carbamoyl phosphate synthetase 1 (CPS1) deficiency due to CPS1 mutations is a rare autosomal-recessive urea cycle disorder causing hyperammonemia that can lead to death or severe neurological impairment. CPS1 catalyzes carbamoyl phosphate formation from ammonia, bicarbonate and two molecules of ATP, and requires the allosteric activator N-acetyl-L-glutamate. Clinical mutations occur in the entire CPS1 coding region, but mainly in single families, with little recurrence. We characterized here the only currently known recurrent CPS1 mutation, p.Val1013del, found in eleven unrelated patients of Turkish descent using recombinant His-tagged wild type or mutant CPS1 expressed in baculovirus/insect cell system. The global CPS1 reaction and the ATPase and ATP synthesis partial reactions that reflect, respectively, the bicarbonate and the carbamate phosphorylation steps, were assayed. We found that CPS1 wild type and V1013del mutant showed comparable expression levels and purity but the mutant CPS1 exhibited no significant residual activities. In the CPS1 structural model, V1013 belongs to a highly hydrophobic ß-strand at the middle of the central ß-sheet of the A subdomain of the carbamate phosphorylation domain and is close to the predicted carbamate tunnel that links both phosphorylation sites. Haplotype studies suggested that p.Val1013del is a founder mutation. In conclusion, the mutation p.V1013del inactivates CPS1 but does not render the enzyme grossly unstable or insoluble. Recurrence of this particular mutation in Turkish patients is likely due to a founder effect, which is consistent with the frequent consanguinity observed in the affected population.
Assuntos
Carbamoil-Fosfato Sintase (Amônia)/genética , Doença da Deficiência da Carbamoil-Fosfato Sintase I/genética , Deleção de Sequência , Animais , Carbamoil-Fosfato Sintase (Amônia)/química , Carbamoil-Fosfato Sintase (Amônia)/metabolismo , Estabilidade Enzimática , Feminino , Efeito Fundador , Humanos , Recém-Nascido , Masculino , Estrutura Terciária de Proteína , Proteínas Recombinantes de Fusão , Células Sf9 , Spodoptera , TurquiaRESUMO
Inflammasomes are innate immune sensing and signaling complexes critical for defense against pathogens and response to cellular stresses. A core component of inflammasomes is the sensor protein, which, upon sensing pathogen- or danger-associated molecular patterns (PAMPs or DAMPs), converts from inactive to active signaling platform for initiation of inflammatory signaling. A reliable source for the production and purification of recombinant inflammasome sensors is therefore invaluable for biochemical and structural characterizations, as well as drug screening for the development of therapeutics. Here, we describe an expression and purification protocol using the baculovirus-insect cell expression system to generate recombinant NLRP1, an important member of the NOD-like receptor (NLR) family of inflammasome sensors.
Assuntos
Inflamassomos , Proteínas NLR , Inflamassomos/metabolismo , Proteínas NLR/genética , Transdução de Sinais , Baculoviridae/genética , Baculoviridae/metabolismo , Proteína 3 que Contém Domínio de Pirina da Família NLRRESUMO
Cell lines derived from Spodoptera frugiperda (Sf), which are the most widely used hosts in the baculovirus-insect cell system, are contaminated with Sf-rhabdoviruses (Sf-RVs). In this study, we identified a closely related virus (Sf-CAT-RV) in the caterpillar species used to isolate the original Sf cell line. We then evaluated the Sf-RV and Sf-CAT-RV host ranges, found Sf-CAT-RV could infect Vero cells, and obtained results suggesting both variants can infect mouse ear fibroblasts. In addition, we found both variants could establish pantropic infections in severely immunocompromised (RAG2/IL2RG-/-) mice. However, both variants were cleared by two weeks post-inoculation and neither produced any symptoms or obvious adverse outcomes in these hosts. We conclude the caterpillars used to isolate Sf21 cells were the most likely source of the Sf-RV contaminant, Sf-RVs and their Sf-CAT-RV progenitor have broader host ranges than expected from previous work, but neither variant poses a serious threat to human health.
Assuntos
Especificidade de Hospedeiro , Rhabdoviridae , Spodoptera , Rhabdoviridae/fisiologia , Spodoptera/virologia , Linhagem Celular , Animais , Camundongos , Células Vero , Larva/virologia , Chlorocebus aethiops , Hospedeiro Imunocomprometido , Receptores de Interleucina-2/genética , Proteínas de Ligação a DNA/genéticaRESUMO
Respiratory syncytial virus (RSV) is a serious respiratory pathogen in infants and young children worldwide. Currently, no licensed RSV vaccines are available. In this study, we explored stable prefusion conformation virus-like particles (Pre-F VLPs) as RSV vaccine candidates. RSV fusion (F) protein mutants were constructed to form stabilized Pre-F or postfusion (Post-F) configurations. VLPs containing Pre-F or Post-F protein were generated using a recombinant baculovirus (rBV)-insect cell expression system. The assembly and immunological properties of Pre-F or Post-F VLPs were investigated. Pre-F and Post-F VLPs contained antigenic sites Ø and I of pre- and postfusion conformations, respectively. Compared with Post-F VLPs, immunization with Pre-F VLPs elicited upregulation of IFN-γ, IL-2 and IL-10 and downregulation of IL-4 and IL-5 cytokine production in mice. A high percentage of CD25+ Foxp3+ cells or a low percentage of IL-17A-producing cells among CD4+ T cells was observed in the lungs of mice vaccinated with Pre-F VLPs. Importantly, immunization with Pre-F VLPs induced a high level of RSV neutralizing antibody and a balanced immune response, which protected mice against RSV infection without evidence of immunopathology. Our results suggested that Pre-F VLPs generated from rBV-insect cells represent promising RSV vaccine candidates.
Assuntos
Infecções por Vírus Respiratório Sincicial , Vacinas contra Vírus Sincicial Respiratório , Vírus Sincicial Respiratório Humano , Camundongos , Animais , Infecções por Vírus Respiratório Sincicial/prevenção & controle , Vacinas contra Vírus Sincicial Respiratório/genética , Anticorpos Neutralizantes , Vírus Sincicial Respiratório Humano/genética , Anticorpos Antivirais , ImunidadeRESUMO
The baculovirus expression system has been used extensively for the expression of recombinant proteins in insect cells.Recently,recombinant baculoviruses containing mammalian cell-active promoter element have been used to transduce a broad spectrum of primary and established mammalian cells,including non-hepatic cells.Recombinant baculoviruses have been used successfully for transient or stable gene delivery in mammalian cells in vitro,while the efficiency of delivering gene in vivo is inhibited obviously by complements,but efforts have been made to overcome the problems,for instance,VSV-G-pseudotyped baculoviruses display complement resistance.The mechanism of the transduction is still not clearly understood,though many researches have been done.The baculovirus is able to replicate only in insect cells,but it is incapable of initiating replication cycle in mammalian cells,which guarantees high biosafety of this gene delivery system.In addition,this system is easily manipulated and able to carry large inserts.These attributes will undoubtedly lead to the increased application and continued development of this system for highly effective gene delivery into mammalian cells.